The invention pertains to a process for making ceramics, as well as a ceramic article of manufacture.
More specifically, the invention pertains to a process for making a ceramic cutting tool that includes silicon nitride-based cutting tools, SiAlON-based cutting tools, alumina-based cutting tools, titanium carbonitride-based cutting tools, and ceramic whisker-reinforced ceramic cutting tools, such as, for example, a whisker-reinforced titanium carbonitride-based ceramic cutting tool and a whisker-reinforced alumina-based ceramic cutting tool.
Heretofore, silicon nitride-based cutting inserts, and SiAlON-based cutting inserts, which are ceramic articles of manufacture, have been shown to be useful for many material removal applications. U.S. Pat. No. 4,127,416 to Lumby et al., U.S. Pat. No. 4,563,433 to Yeckley et al., U.S. Pat. No. 4,711,644 to Yeckley et al., U.S. Pat. No. 5,370,716 to Mehrotra et al., U.S. Pat. No. 5,382,273 to Mehrotra et al., U.S. Pat. No. 5,525,134 to Mehrotra et al., U.S. Pat. No. 4,880,755 to Mehrotra et al., and U.S. Pat. No. 4,913,936 to Mehrotra et al. disclose various SiAlON and silicon nitride compositions which are useful as cutting inserts. These patents are hereby incorporated by reference herein.
Heretofore, whisker-reinforced cutting inserts, which are also ceramic articles of manufacture, have also been shown to be useful for material removal application. These whisker-reinforced cutting inserts include alumina-based materials reinforced with silicon carbide whiskers such as shown and described in U.S. Pat. No. B2 4,789,277 to Rhodes et al. and U.S. Pat. No. 4,961,757 to Rhodes et al. wherein these Rhodes et al. patents are hereby incorporated by reference herein. A whisker-reinforced alumina-based cutting insert with a zirconia addition is also shown and described in U.S. Pat. No. 4,959,332 to Mehrotra et al. wherein this patent is hereby incorporated by reference herein. A whisker-reinforced titanium carbonitride-based cutting insert is shown and described in PCT Patent Application No. PCT/US96/15192 (International Filing Date of Sep. 20, 1996) [International Publication No. WO 97/18177 published on May 22, 1997] for a WHISKER REINFORCED CERAMIC CUTTING TOOL AND COMPOSITION THEREOF [as well as in U.S. patent application Ser. No. 08/874,146 filed Jun. 13, 1997 to Mehrotra] wherein these patent applications are hereby incorporated by reference herein.
While the cutting inserts made from the materials of the above patents and patent application exhibit an acceptable performance in material removal applications such as, for example, milling and turning, there remains as an objective the production of ceramic cutting inserts (e.g., silicon nitride-based cutting inserts, SiAlON-based cutting inserts, alumina-based cutting inserts, titanium carbonitride-based cutting inserts, and whisker-reinforced ceramic cutting inserts) with still better performance characteristics in material removal applications. There also remains as an objective the production of ceramic cutting inserts (e.g., silicon nitride-based cutting inserts, SiAlON-based cutting inserts, alumina-based cutting inserts, titanium carbonitride-based cutting inserts, and whisker-reinforced ceramic cutting inserts) that exhibit a microstructure that results in better physical properties and performance characteristics.
In one form thereof, the invention is a process for making a heat treated ground ceramic cutting insert comprising the steps of: providing an uncoated ground ceramic cutting insert having at least a portion thereof being ground; and heat treating the uncoated ground ceramic cutting insert so as to form the heat treated ground ceramic cutting insert.
In another form thereof, the invention is a heat treated ground ceramic cutting insert produced by the process comprising the steps of: providing an uncoated ground ceramic cutting insert having at least a portion thereof being ground; and heat treating the ground ceramic cutting insert so as to form the heat treated ground ceramic cutting insert.
In still another form thereof, the invention is a heat treated ground ceramic article of manufacture formed in the presence of a reaction source wherein the article of manufacture comprises a substrate which has a surface. The substrate presents a microstructure wherein there is a surface region extending inwardly from the surface of the substrate, and there is a bulk region inwardly of the surface region. The bulk region has a bulk composition. The surface region has a surface composition resulting from a reaction with the reaction source wherein the surface composition is different from the bulk composition.
In yet another form thereof, the invention is a process for making a heat treated ground ceramic article of manufacture comprising the steps of: providing an uncoated ground ceramic compact having at least a portion thereof being ground; and heat treating the uncoated ground ceramic compact so as to form the heat treated ground ceramic article of manufacture.